While international attention focuses on the widespread fires causing air pollution in Southeast Asia, a less obvious health threat is sickening thousands of Asians. Hazardous waste threatens millions of people in Asia, a booming region that seems intent on industrializing at almost any cost. More and more such wastes, sometimes called toxic wastes, are being produced and released into the environment, triggering severe health problems. Asia's high population density and often tropical climate put it especially at risk for contamination. But while regulations have increased, enforcement is inadequate and often undermined by corruption. Asian governments seem to believe that cleanup can come after economic development. The U.S. experience, however, shows that it is a matter of pay now, or pay much more later. Meanwhile, even as public outcry grows over highly toxic sites and industries, a new wave of health problems is raising concerns about far more subtle poisons. Unless serious action is taken soon, the costs to human health and the environment-which are already incalculable-will continue to escalate.